There is a problem in that the meter gets its voltage from the middle of the loom - hence why I wired it directly to the battery terminal - via a "ignition on" relay - you can wire the relay to the "normal" gauge supply. Calibrating the meter for the full load situation will only make it read wrong ( high ) when the load ( no fans or lights etc ) is low.

Under what circumstances do you calibrate it Jim - everything off or everything on. Given the wiring loom and resistance therein you will get a different result. Wiring direct to the battery will give the same result everything off and everything on.

I always thought calibration meant it was right within a certain range (i.e. 10-90% of FSD)? Should be reasonably easy to calibrate it to read the correct voltage at 1) Ignition on, engine and everything else off (about 12.5V?) and 2) Engine running and charging battery (all other equipment off) - about 13.8-14.4V? Anything lower is definite discharge and anything higher indicates a charging fault.

Phil Howard
Scimitarweb Forum Admin
SS1 1600 Rooster Turbo; Sabre Mk1.5, Sabre Mk2
Previous: SE5/5a/SS1 No.1/SS1 Rooster/SS1 1800Ti/SE5a 24 Valvehttp://www.ss1turbo.comNever try and argue with an idiot. They drag you down to their level, then beat you based on experience.

Then it will read low on load which can be worrying - our 6A would go down to 11v with the heater fan lights etc were on when the voltage on the battery terminals was 13v hence I changed the wiring. If you want it to read the battery voltage ( which is what it is for ) then wire it directly to the battery ( via a relay ). If you don't believe me then check its reading with everything on then remove the green wire from it and replace it with a wire to the battery - compare results.

If the voltmeter was supposed to just read the battery voltage it probably would have been wired to the battery. By reading system voltage it tells you if there’s other problems, long before it gets bad enough to register at the battery (particularly as its being charged by the alternator).

The standard system shouldn’t read 13v off load and drop to 11 on full load - that’s proving my point exactly.

You obviously believe that the voltage drop from the battery to the point where the gauge is connected is zero, maybe close to zero but not when a load is applied.Its a lot easier to connect the gauge to a close by wire. You have not proved your point - basic electrics.